Device and method for drying  fluids conducted in closed circuits

ABSTRACT

A device for drying fluids conducted in a closed circuit provides a bypass line which can be switched in parallel to a pipe of the closed circuit that conducts a fluid via a first valve and a second valve. A first demoisturizer may be disposed in the bypass line. A method for drying fluids conducted in closed circuits is also provided. Part of the fluid may be directed from the pipe of the closed circuit into the bypass line connected in parallel to the pipe of the closed circuit and dried using the device according to the system described herein.

The present invention relates to a device for drying fluids circulating in closed circuits and a method for drying fluids circulating in closed circuits.

Fluids are circulated in closed circuits in various applications, it being essential that the fluids are dry.

Moisture, in particular water in refrigerants in refrigeration systems, represents a serious problem for the operational capability of the refrigeration system. On the one hand, important components may become iced and frozen, which prevents the refrigerant from flowing. On the other hand, water in conjunction with refrigerant oil results in the formation of acids, which may cause acid corrosion and occasionally burnout of the compressor present in the refrigeration system. Therefore, it is necessary to reduce the moisture content in the refrigeration circuit and to keep it as low as possible during the operation of the system.

It is known to shut down the entire refrigeration system and then to remove and dispose of all the refrigerant present in the refrigeration system, to dry the system using nitrogen, and to fill it again using dry refrigerant. A procedure of this type results in the refrigeration system being entirely down for a longer time and, on the other hand, high costs being incurred because the refrigerant must be fully replaced and, in addition, disposed of.

It is furthermore known to install a demoisturizer in the form of a moisture filter in a line of the refrigeration system conducting the refrigerant, in particular upstream from a compressor. The refrigerant thus flows through the moisture filter, which filters out the moisture, which is thus enriched in the moisture filter. The moisture filter must be monitored to prevent the moisture filter from becoming fully saturated, which may result in water breakthrough. The moisture filter must therefore be replaced regularly, which also results in downtime of the refrigeration system and is associated with high labor costs.

The object of the present invention is therefore to provide a device and a method for drying fluids circulating in closed circuits which makes it possible to continuously dry the fluid during ongoing operation of the closed circuit and thus avoids high expenditures in terms of time and costs.

The object is achieved according to the present invention by using a device for drying fluids circulating in closed circuits having the features of Patent Claim 1, and a method for drying fluids circulating in closed circuits having the features of Patent Claims 26 or 27.

The subclaims provide advantageous embodiments and refinements of the present invention.

The device according to the present invention for drying fluids circulating in closed circuits is based on providing a bypass line which is switchable via a first valve and a second valve parallel to a fluid-conducting line of the closed circuit. A portion of the fluid flowing through the closed circuit is thus deviated into the bypass line. According to the present invention, a first demoisturizer, which removes the moisture from the fluid, is situated in the bypass line. Since the demoisturizer is no longer situated directly in the closed circuit, if the demoisturizer has to be replaced, the bypass line may be closed to the closed circuit via the first and second valves, whereupon the demoisturizer may be removed from the bypass line and replaced with a new or cleaned demoisturizer.

In an advantageous refinement of the present invention, a second demoisturizer is situated in the bypass line downstream from the first demoisturizer, the second demoisturizer being able to take up the moisture not taken up by the first demoisturizer, to improve the effectiveness of the fluid drying.

In a particularly preferred specific embodiment of the present invention, a third valve is situated between the first valve and the first demoisturizer, and a fourth valve is situated between the second demoisturizer and the second valve, either the first demoisturizer or the second demoisturizer being switchable downstream from the valve via the third valve in the direction of flow, and either the second demoisturizer or the first demoisturizer being switchable upstream from the second valve via the fourth valve, so that when the fluid flows from the third valve to the fourth valve, it flows either first through the first demoisturizer and then through the second demoisturizer or, alternatively, first through the second demoisturizer and then through the first demoisturizer.

The first and/or second demoisturizer(s) may be designed as moisture exchanger(s), moisture filter(s), or also as moisture filter(s) having integrated moisture exchanger(s). In one specific embodiment, the first demoisturizer is designed as a moisture filter and the second demoisturizer is designed as a moisture exchanger, or the first and/or second demoisturizer(s) is/are designed as moisture filter(s) having integrated moisture exchanger(s), to first enrich the moisture in the moisture filter during the operation of the closed circuit and subsequently, when a certain degree of saturation has been reached in the moisture filter, to be able to heat the moisture filter, for example, and discharge the moisture out of the closed circuit and the bypass line to the outside via the moisture exchanger without affecting, in particular shutting off, the closed circuit or opening the bypass circuit. The moisture exchanger thus has the advantage that moisture may be discharged from the closed circuit without downtime of the circuit, the moisture exchanger needing a certain moisture gradient for effective water discharge. This is achieved by combining the moisture exchanger with a moisture filter, which first enriches the moisture and then releases a large quantity of it in a controlled manner, so that a high moisture gradient is obtained across the moisture exchanger and the moisture exchanger effectively discharges the moisture.

In a particularly preferred specific embodiment of the present invention, the first and second demoisturizers are designed as moisture filters, while another demoisturizer in the form of an additional moisture exchanger is situated between the two moisture filters. In particular with the possibility of modifying the direction of flow via the bypass line, this construction makes it possible to first accumulate most of the moisture in one of the two demoisturizers, which are designed as moisture filters, for example, in the first demoisturizer, while the other, for example, the second demoisturizer, filters out the residual moisture from the fluid and subsequently, when the degree of saturation in the first demoisturizer has been reached, makes the first demoisturizer release water in a controlled manner, for example, via heating, to then discharge the moisture via the moisture exchanger situated downstream from the first demoisturizer, the second demoisturizer being able to continue to filter out the residual moisture that is not discharged via the moisture exchanger. The direction of flow may be subsequently modified, so that the second demoisturizer removes most of the moisture from the fluid, which makes it possible to achieve maximally effective drying and maximum moisture discharge.

If the fluid only flows past the moisture exchanger, this means a very low water content, so that the moisture gradient is relatively small and the moisture exchanger cannot operate in an optimum or effective manner. Therefore a device for generating a moisture gradient is situated preferably on the side of the moisture exchanger facing away from the closed circuit. In one specific embodiment, this device may be designed as a device for generating a vacuum. Alternatively, the device for generating a moisture gradient is designed as a drying agent supply device, which conducts a drying agent past the moisture exchanger into a drying agent discharge device. The drying agent may be air or nitrogen, for example. The drying agent is preferably further demoisturized via another device.

For this purpose, in a preferred specific embodiment, a third demoisturizer, which removes moisture from the drying agent, is situated between the drying agent supply device and the moisture exchanger, so that the moisture gradient across the moisture exchanger is increased.

A fourth demoisturizer may be preferably situated between the moisture exchanger and the drying agent discharge device, which also removes the moisture again from the drying agent which has been taken up by the drying agent at the moisture exchanger and removed from the closed circuit, in particular if the drying agent is directed past the moisture exchanger again.

In a particularly preferred specific embodiment of the present invention, a fifth valve is situated between the drying agent supply device and the third demoisturizer, and a sixth valve is situated between the fourth demoisturizer and the drying agent discharge device, either the third demoisturizer or the fourth demoisturizer being switchable downstream from the drying agent supply device via the fifth valve in the direction of flow, and alternatively either the fourth demoisturizer or the third demoisturizer being switchable upstream from the drying agent discharge device via the sixth valve, so that when the fluid flows from the drying agent supply device to the drying agent discharge device, it flows either first through the third demoisturizer and then through the fourth demoisturizer or, alternatively, first through the fourth demoisturizer and then through the third demoisturizer. A particularly effective drying of the drying agent is thus possible also in the drying agent circuit as described previously. However, even if the drying agent is not circulated, this design ensures that a demoisturizer is basically situated upstream from the moisture exchanger in both directions of flow to thus ensure that dry drying agent is conducted to the moisture exchanger and thus the moisture gradient is increased and that, on the other hand, each demoisturizer may be switched upstream from the drying agent discharge device to dry the demoisturizer, so that when the demoisturizer is heated, the moisture may be conducted directly into the drying agent discharge device without being directed past the moisture exchanger to there reduce the moisture gradient or even introduce moisture into the closed fluid circuit.

In a preferred specific embodiment in particular, the third and/or fourth demoisturizer(s) is/are designed as moisture filters.

The moisture filters are preferably designed as zeolith filters to ensure effective enrichment of the moisture in the filter.

To drive out the moisture from the demoisturizers without replacing the demoisturizers, the different demoisturizers are preferably heatable. For the same reason, the additional moisture exchanger, if present, is also heatable.

The moisture exchanger is preferably designed as a moisture-permeable diaphragm, in particular as a Nafion diaphragm or as a zeolith molecular sieve to ensure that water, but not the fluid or the drying agent, may pass through the diaphragm. In an alternative specific embodiment, the moisture exchanger is designed as a porous ceramic tube having a zeolith coating. On the one hand, the zeolith coating absorbs the moisture, but it also allows the moisture to pass through. In a preferred specific embodiment, the ceramic tube is filled with a zeolith granulate to enhance the storage capacity for moisture and thus to form a combined moisture filter having an integrated moisture exchanger. The ceramic is a PTC ceramic, for example, which has the advantage that it may also be used for heating, in addition to its support function.

To maintain the continuous flow of fluid through the bypass line, the bypass line is preferably switched to a pipe of the closed circuit conducting fluid, which has a compressor. This generates the appropriate pressure gradient, which maintains the necessary fluid flow.

To check how effectively the particular demoisturizers have demoisturized the fluid, a moisture sensor is placed in the bypass line, preferably downstream from the first demoisturizer, in particular upstream from the point where the fluid is returned into the closed circuit.

Particularly preferably, the fluid is a refrigerant and/or the closed circuit is designed as a refrigeration system, since refrigerants should contain no moisture in order to ensure reliable operation of the refrigeration system.

The method according to the present invention for drying fluids circulating in closed circuits is based on diverting a part of the fluid from a fluid-conducting pipe of the closed circuit into a bypass line connected in parallel to the pipe conducting the fluid. A device for drying a fluid according to the present invention, using which moisture is removed from the fluid, is situated in the bypass line. By situating the device in a bypass line it is possible, on the one hand, to dry the fluid during the operation of the closed circuit, and, on the other hand, to service and replace a defective device for drying a fluid or a device for drying a fluid in which a demoisturizer is saturated.

In the method according to the present invention a device for drying a fluid having at least one first demoisturizer, which is designed as a moisture filter, and at least one other demoisturizer, which is designed as a moisture exchanger, is preferably situated in the bypass line; of course, the moisture filter and the moisture exchanger may also be situated integrated in a demoisturizer. When a defined moisture threshold value is reached, the moisture filter is heated to drive out the moisture accumulated in the moisture filter and to discharge it via the moisture exchanger. This makes it possible that the bypass line does not have to be opened for removing the moisture, which has accumulated in a demoisturizer in the bypass line, from the bypass line. In particular, no fluid escapes from the bypass line to the environment, so that no costs arise for disposing of the fluid.

A second demoisturizer, which is designed as a moisture filter and is capable of taking up the moisture not filtered out by the first moisture filter, thus increasing the degree of drying, is preferably situated in the bypass line.

A third valve is preferably situated between the first valve and the first demoisturizer, and a fourth valve is situated between the second demoisturizer and the second valve, either the first demoisturizer or the second demoisturizer being switchable downstream from the first valve via the third valve in the direction of flow, and either the second demoisturizer or the first demoisturizer being switchable upstream from the second valve via the fourth valve, so that when the fluid flows from the third valve to the fourth valve, it flows either first through the first demoisturizer and then through the second demoisturizer or, alternatively, first through the second demoisturizer and then through the first demoisturizer. This makes it possible to reverse the direction of flow. A change in the direction of flow is preferably provided after the moisture filter has been heated to drive out the accumulated moisture to ensure maximum exchange and the most effective possible drying both of the drying agents and of the demoisturizers.

In a preferred specific embodiment of the method, the moisture gradient is increased for optimum operation of the moisture exchanger by placing a device for generating a moisture gradient on the side of the moisture exchanger facing away from the closed circuit.

The present invention is described in greater detail with reference to the figures below.

FIG. 1 shows a schematic view of a first exemplary embodiment of the present invention;

FIG. 2 shows a schematic view of a second exemplary embodiment of the present invention;

FIG. 3 shows a schematic view of a third exemplary embodiment of the present invention;

FIG. 4 shows a schematic view of a fourth exemplary embodiment of the present invention; and

FIG. 5 shows a schematic view of a fifth exemplary embodiment of the present invention.

FIGS. 1 through 5 show different exemplary embodiments of the present invention, the same reference numerals identifying the same components.

FIG. 1 shows a first exemplary embodiment of a device for drying a fluid circulating in a closed circuit. The closed circuit is designed, for example, as a refrigeration system in which a refrigerant is circulated as the fluid. In FIG. 1, a pipe 10, which conducts a refrigerant, is illustrated as a component of a refrigeration system. A compressor 15, which maintains and, if necessary, regulates, the velocity of the flow is situated in pipe 10 conducting the refrigerant. Situated parallel to pipe 10 is a bypass line 20, which is connected to pipe 10 via a first valve V1 and a second valve V2 and may also be completely isolated from pipe 10 via these two valves V1, V2. A portion of the refrigerant circulating in pipe 10 flows through first valve V1 into bypass line 20 when this valve V1 is open. The refrigerant flow in bypass line 20 should possibly amount to less than 5% of the total flow of refrigerant and, in particular, should not exceed 10% of the total mass flow in order to disturb the refrigerant flow in the refrigeration system as little as possible. A throttle valve 24, which is used for regulating the mass flow through bypass line 20, is situated downstream from first valve V1. The direction of flow of the refrigerant is indicated by the outlined arrows in FIG. 1.

A first demoisturizer E1, through which the refrigerant flows, is situated in bypass line 20. The first demoisturizer may be, in principle, a moisture exchanger or, as illustrated in FIG. 1, a moisture filter, in particular a zeolith filter 50. This moisture filter has a housing E1 a, which is sealed to the outside. Neither refrigerant nor moisture may thus escape from housing E1 a of first demoisturizer E1. The refrigerant is dried in first demoisturizer E1, the moisture being enriched in zeolith filter 50. The refrigerant thus dried flows on through bypass line 20 toward second valve V2, to enter pipe 10 of the refrigeration system again downstream from second valve V2. Before the refrigerant enters pipe 10, in particular upstream from second valve V2, there is a moisture sensor 22, which checks the degree of drying reached by the refrigerant. In particular, the operation of first demoisturizer E1 may also be checked using moisture sensor 22. Since the moisture accumulates in first demoisturizer E1, in particular in zeolith filter 50, the moisture content of zeolith filter 50 increases. In the event of high water content in zeolith filter 50, there is the risk of a water breakthrough. The water content of zeolith filter 50 must therefore be monitored, preferably via an appropriately integrated sensor. Zeolith filter 50 must be replaced in regular intervals to prevent a water breakthrough. For that purpose, valves V1, V2 are closed, so that bypass line 20 may be opened without disturbing the operation of the refrigeration system. Subsequently first demoisturizer E1 may be removed and replaced by a new demoisturizer or reinstalled after cleaning and drying. By monitoring the water content using a moisture sensor 22 or similar means for detecting the saturation state of zeolith filter 50, a stop of the flow through bypass line 20 may also be triggered automatically by activating valves V1, V2. Closing valve V2 is sufficient in this case

Since in this specific embodiment a refrigerant in bypass line 20 must be disposed of at an additional cost, in a second specific embodiment of the invention, which is illustrated in FIG. 2, another demoisturizer E5 is installed in bypass line 20. Demoisturizer E5 is designed as a moisture exchanger 30. Moisture may be removed from the system facing the refrigeration system and bypass line 20 using a moisture exchanger 30 via a moisture-permeable layer, in particular a moisture-permeable diaphragm 32, without having to open bypass line 20 to the outside. Refrigerant, however, cannot pass through moisture-permeable diaphragm 32, so that there is no risk that the refrigerant may escape from bypass line 20. Moisture exchanger 30 operates in such a way that in the event of a sufficiently high moisture gradient between the two sides of moisture-permeable diaphragm 32, moisture diffuses through the diaphragm and may be discharged on the other side. Moisture-permeable diaphragm 32 may be made of Nafion or zeolith.

In the present second exemplary embodiment, most of the moisture contained in the refrigerant may be collected in zeolith filter 50 via first demoisturizer E1. Further residual moisture may be removed via the additional demoisturizer E5, in particular if the gradient is sufficiently high, for example, because first demoisturizer E1 has reached its degree of saturation. If first demoisturizer E1 has reached its degree of saturation, the flow rate is strongly throttled via throttle valve 24, and first demoisturizer E1 is heated via a heating terminal E1 b, so that the moisture is driven out of zeolith filter 50 again. A high amount of water is thus released within a short period, which reaches the additional demoisturizer E5, i.e., moisture exchanger 30, connected downstream from first demoisturizer E1. This creates a high gradient across the diaphragm of additional demoisturizer E5, so that the moisture may be effectively discharged from bypass line 20 via moisture exchanger 30. After complete removal of moisture by heating zeolith filter 50, zeolith filter 50 is suitable again for removing moisture from the refrigerant, so that throttle valve 24 may be opened again to increase the flow again, and more refrigerant from the refrigeration system may be dried. The operation of the refrigeration system does not need to be stopped at any time.

It is important, however, that in this specific embodiment attention must be paid that no concentrated water is returned to the refrigeration system. This may occur if water is driven out by heating zeolith filter 50, but moisture exchanger 30 does not discharge all the water. This is prevented by completely closing valve V2 and preferably also valve V1 during the moisture removal by heating. Since a higher pressure builds up in bypass line 20 during moisture removal by heating if valves V1, V2 are closed, it may be necessary to provide a pressure equalizing valve. Alternatively a second demoisturizer, which is designed as a moisture filter like first demoisturizer E1 and removes the moisture from the refrigerant that is not discharged via moisture exchanger 30, may be connected downstream from moisture exchanger 30.

Particularly preferably, moisture exchanger 30 is integrated into first demoisturizer E1 to remove the moisture from the refrigerant even more effectively.

FIG. 3 shows a third exemplary embodiment of a device for drying refrigeration systems, the same components as in the exemplary embodiments of FIGS. 1 and 2 being labeled with the same reference numerals.

First demoisturizer E1, a second demoisturizer E2, and, between the two demoisturizers E1, E2, additional demoisturizer E5, which is designed as moisture exchanger 30, are situated in bypass line 20. First demoisturizer E1 and second demoisturizer E2 are designed as moisture filters, in particular as zeolith filters 50. In particular, second demoisturizer E1 also has a housing E1 a and a heating terminal E1 b. In the case of a flow direction along the outlined arrows, the fluid flows from first valve V1 first through first demoisturizer E1, then through moisture exchanger 30 and then through second demoisturizer E2 before the refrigerant is transferred again into pipe 10 of the refrigeration system through second valve V2. In this specific embodiment, however, a third valve V3 is additionally situated between first valve V1 and first demoisturizer E1 and a fourth valve V4 is situated between second demoisturizer E2 and second valve V2. Third valve V3 and fourth valve V4 are three-way valves, so that either first demoisturizer E1 or second demoisturizer E2 may be switched downstream from first valve V1 via third valve V3 and alternatively second demoisturizer E2 or first demoisturizer E1 may be switched upstream from second valve V2 via fourth valve V4. This makes it possible to reverse the direction of flow between third valve V3 and fourth valve V4 through bypass line 20, so that either the refrigerant flows initially through first demoisturizer E2 and then second demoisturizer E2 along the outlined arrows of FIG. 3, or, alternatively, the flow initially passes through second demoisturizer E2 and then through first demoisturizer E1 along the solid arrows in FIG. 3. In particular in combination with the additional moisture exchanger 30 situated between the two demoisturizers E1, E2, the following preferred mode of operation results. Initially, the refrigerant flows along the outlined arrows first through first demoisturizer E1, in which most of the moisture contained in the refrigerant is removed from the refrigerant by zeolith filter 50. This moisture is stored in zeolith filter 50. The residual moisture may then be effectively removed from the refrigerant via additional moisture exchanger 30 if the moisture gradient is sufficiently high, or via second demoisturizer E2, so that an increased degree of drying of the refrigerant is achieved. The moisture in the refrigerant is checked via moisture sensor 22. With the aid of additional sensors on demoisturizers E1, E2, the degree of saturation already reached by first demoisturizer E1 may be checked. If the corresponding degree of saturation of demoisturizer E1 has been reached, the refrigerant flow rate may be reduced by throttling or stopped via throttle valve 24; first valve V1 and second valve V2 may also be closed, if necessary, for greater safety. Demoisturizer E1 is then heated up via heating terminal E1 b, for example, to approximately 200° C. The heating drives the accumulated water out of zeolith filter 50 of first demoisturizer E1, transporting it to moisture exchanger 30, where there is a sufficiently high moisture gradient for effectively discharging the water via moisture exchanger 30. If necessary, the residual moisture remaining in the refrigerant is taken up via second demoisturizer E2. After first demoisturizer E1 has thus been dried, third valves V3 and fourth valve V4 are switched in such a way that subsequently the fluid flows through the bypass line along the solid arrows and thus in the opposite direction through the section of bypass line 20 between third valve V3 and fourth valve V4, so that the refrigerant may flow initially through second demoisturizer E2 and then through the additional moisture exchanger 30 and finally through first demoisturizer E1. This now loads second demoisturizer E2 predominantly with water from the refrigerant, while the additional moisture exchanger 30 assumes barely any function and first demoisturizer E1 takes up the residual moisture from the refrigerant. In this way, maximum exchange and the most effective possible degree of drying of the refrigerant, as well as a high degree of drying of demoisturizers E1, E2 are achieved without having to open bypass line 20 or even the refrigeration system. In particular, the operation of the refrigeration system does not have to be stopped.

In the exemplary embodiments illustrated in FIG. 3, the water is discharged via moisture exchanger 30 in such a way that it drips from moisture-permeable diaphragm 32 to the outside, for example, or fumigates. Diaphragm 32 is designed in such a way that it is permeable to water only, but not for the refrigerant flowing through the refrigeration system, and may be manufactured from Nafion, for example, or designed as a zeolith molecular sieve.

To increase the moisture gradient across diaphragm 32, a device for generating a vacuum may be situated on the side of diaphragm 32 facing away from the refrigeration system, so that the moisture gradient is increased and more water passes through diaphragm 32 to the outside. Alternatively, a drying agent may also be directed past the side of diaphragm 32 facing away from the refrigeration system to increase the moisture gradient. This may be achieved, for example, by using a fifth specific embodiment of the present invention, as illustrated in FIG. 5. In this exemplary embodiment, a drying agent supply device is situated on the side of diaphragm 32 facing away from the refrigeration system, which may be, for example, a device for providing a compressed gas such as nitrogen or air via a gas supply 41 or an ambient air supply 42 with the aid of a suitable compressor. Drying agent supply device 40 directs the appropriate drying agent, for example, a gas such as nitrogen or air, past the side of diaphragm 32 of additional moisture exchanger 30 facing away from the refrigeration system into a drying agent discharge device 44. To keep the drying agent in circulation, the drying agent having reached drying agent discharge device 44 may be returned to the drying agent supply device. However, the drying agent may also be discharged after a single use.

A third demoisturizer E3, which is preferably also designed as a moisture filter, in particular as a zeolith filter 50, is situated between drying agent supply device 40 and diaphragm 32. Third demoisturizer E3 also has a housing E3 a and a heating terminal E3 b. The drying agent supplied is additionally demoisturized in zeolith filter 50 before it is conducted to diaphragm 32 to further increase the moisture gradient across diaphragm 32.

A fourth demoisturizer E4, which is preferably also designed as a moisture filter, in particular as a zeolith filter 50, is situated between diaphragm 32 and drying agent discharge device 44. Fourth demoisturizer E4 also has a housing E4 a and a heating terminal E4 b.

A fifth valve V5 is situated between drying agent supply device 40 and third demoisturizer E3, while a sixth valve V6 is situated between fourth demoisturizer E4 and drying agent discharge device 44. Fifth valve V5 and sixth valve V6 are also designed as three-way valves, so that third demoisturizer E3 or fourth demoisturizer E4 may be switched downstream from drying agent supply device 40 via fifth valve V5, while alternatively fourth demoisturizer E4 or third demoisturizer E3 may be switched upstream from drying agent discharge device 44 via sixth valve V6. This makes it possible, also in this configuration, as indicated by the outlined and solid arrows, to reverse the direction of flow through the drying agent circuit. Furthermore, third demoisturizer E3 and fourth demoisturizer E4 are designed to be heatable. This makes the following procedure possible for drying the drying agent and for drying third demoisturizer E3 and fourth demoisturizer E4. Initially, the drying agent is conducted into first demoisturizer E3 via drying agent supply device 40 along the outlined arrows, where the drying agent is demoisturized, so that third demoisturizer E3 is loaded with moisture. At diaphragm 32, the drying agent takes up moisture again, which may be filtered out in fourth demoisturizer E4 if the drying agent is to be returned to diaphragm 32. Alternatively, demoisturizer E4 connected downstream from diaphragm 32 may be additionally heated to pass the moisture absorbed by the drying agent through and drive out the already absorbed moisture. Demoisturizers E3, E4 connected downstream from diaphragm 32 may also be completely removed from the drying agent stream using an additional valve in order to thus save heating costs. In principle, it is thus also possible to situate only one demoisturizer in the drying agent circuit.

If one of the two demoisturizers E3, E4 reaches its degree of saturation, valves V5, V6 are switched in such a way that the corresponding demoisturizer E3, E4 is switched upstream from drying agent discharge device 44. The corresponding demoisturizer E3, E4 is then heated up, so that moisture may be discharged toward drying agent discharge device 44 without being directed past diaphragm 32 and there possibly causing moisture to be introduced into bypass line 20.

FIG. 4 shows a fourth exemplary embodiment of the present invention. In this exemplary embodiment, a first demoisturizer E1′ and a second demoisturizer E2′ are situated in bypass line 20. In the case of a flow direction along the outlined arrows, the refrigerant flows from first valve V1 first through first demoisturizer E1′ and then through second demoisturizer E2′, before being supplied again via second valve V2 into pipe 10 of the refrigeration system conducting the refrigerant. Third valve V3 is designed again as a three-way valve and situated between first demoisturizer E1′ and first valve V1, via which alternatively first demoisturizer E1′ or second demoisturizer E2′ may be switched downstream from first valve V1. Fourth valve V4 is also designed as a three-way valve and situated between second demoisturizer E2′ and second valve V2′, via which alternatively first demoisturizer E1′ or second demoisturizer E2′ may be switched upstream from second valve V2, so that if the two valves V3, V4 are appropriately switched, the direction of flow may be reversed in such a way that between the two valves V3, V4 the flow may also take place along the solid arrows in the reverse direction first through second demoisturizer E2′ and then through first demoisturizer E1′.

The two demoisturizers E1′, E2′ are equipped as porous ceramic tube 52 having a zeolith coating 54 on the inside of ceramic tube 52. The zeolith coating ensures that only water may pass through ceramic tube 52, but the refrigerant will flow inside zeolith coating 54 through ceramic tube 52 and thus may not escape from bypass line 20. The ceramic tube is thus used essentially as a support ceramic for zeolith coating 54. If, for example, a PTC ceramic is used as the support ceramic, it may be additionally used for heating. Zeolith coating 54 essentially functions as a moisture exchanger.

First demoisturizer E1′ and second demoisturizer E2′ are located in a chamber 70, in which the moisture having passed through zeolith coating 54 accumulates and which is preferably emptied via a pump 60 during heating to provide a sufficiently high moisture gradient across zeolith coating 54. In particular, the moisture may drip out into a container 62 and be removed via pump 60. In normal operation, pump 60 does not necessarily have to run permanently. However, to prevent moisture from getting from container 62 back into the refrigerant through the zeolith coating, a valve, which is closed during operation and is opened only during moisture removal by heating, is preferably located between chamber 70 and container 62. Since a vacuum is generated by pump 60 in chamber 70 prior to closing the valve, only a very small amount of air is in chamber 70, which causes no significant moisture input back into the refrigerant during operation.

Alternatively, chamber 70 may also be purged using air or another drying agent during normal operation to keep the moisture gradient across zeolith coating 54 sufficiently high. In particular air may be dried again using a device comparable to the device on the side of diaphragm 32 of moisture exchanger 30 facing away from the refrigeration system in the exemplary embodiment illustrated in FIG. 5.

Chamber 70 may have, on the one hand, a water-permeable diaphragm which, on the side facing away from demoisturizers E1′, E2′, may be equipped with an appropriate device for increasing the moisture gradient, so that chamber 70 represents an additional protection wall if refrigerant should escape through zeolith coating 54. Should pores in zeolith coating 54 result in passage of refrigerant, this may be recognized by a pressure increase in chamber 70 during the drying phase, so that the exiting refrigerant may be aspirated dry and collected via another demoisturizer (not depicted) situated in chamber 70.

To further increase the degree of drying of demoisturizers E1′, E2′, a zeolith granulate 56, wetted by the refrigerant flow which thus removes moisture from the refrigerant, is situated in ceramic tube 52. Since zeolith granulate 56 thus functions as a moisture filter, in this specific embodiment demoisturizers E1′, E2′ represent moisture filters having integrated moisture exchangers. When zeolith granulate 56 reaches saturation, first demoisturizer E1′ and second demoisturizer E2′ may be designed to be reheatable to release moisture to the outside via zeolith coating 54 in a controlled manner.

LIST OF REFERENCE NUMERALS

-   10 pipe -   15 compressor -   20 bypass line -   22 moisture sensor -   24 throttle valve -   V1 first valve -   V2 second valve -   V3 third valve -   V4 fourth valve -   V5 fifth valve -   V6 sixth valve -   E1 first demoisturizer -   E1′ first demoisturizer -   E1 a housing -   E1 b heating terminal -   E2 second demoisturizer -   E2′ second demoisturizer -   E2 a housing -   E2 b heating terminal -   E3 third demoisturizer -   E3 a housing -   E3 b heating terminal -   E4 fourth demoisturizer -   E4 a housing -   E4 b heating terminal -   E5 fifth demoisturizer -   30 moisture exchanger -   32 diaphragm -   40 drying agent supply device -   41 gas supply -   42 ambient air supply -   44 drying agent discharge device -   50 zeolith filter -   52 ceramic tube -   54 zeolith coating -   56 zeolith granulate -   60 pump -   62 container -   70 chamber 

1. A device for drying fluids circulating in closed circuits, comprising: a bypass line which is switchable via a first valve and a second valve parallel to a pipe of a closed circuit conducting a fluid; and a first demoisturizer situated in the bypass line.
 2. The device as recited in claim 1, further comprising: a second demoisturizer situated in the bypass line downstream from the first demoisturizer.
 3. The device as recited in claim 2, further comprising: a third valve situated between the first valve and the first demoisturizer; and a fourth valve situated between the second demoisturizer and the second valve, either the first demoisturizer or the second demoisturizer being switchable downstream from the first valve via the third valve in the direction of flow, and either the second demoisturizer or the first demoisturizer being switchable upstream from the second valve via the fourth valve, so that when the fluid flows from the third valve to the fourth valve, the fluid flows either first through the first demoisturizer and then through the second demoisturizer or first through the second demoisturizer and then through the first demoisturizer.
 4. The device as recited in claim 1, wherein the first demoisturizer includes at least one of: a moisture exchanger and a moisture filter.
 5. The device as recited in claim 2, wherein the second demoisturizer includes at least one of: a moisture exchanger and a moisture filter.
 6. The device as recited in claim 2, wherein at least one of: the first demoisturizer and the second demoisturizer includes a moisture filter having an integrated moisture exchanger.
 7. The device as recited in claim 2, wherein the first demoisturizer includes a moisture filter and the second demoisturizer includes a moisture exchanger.
 8. The device as recited in claim 2, wherein the first demoisturizer and the second demoisturizer include moisture filters, and the device further comprising: an additional demoisturizer situated between the first demoisturizer and the second demoisturizer, wherein the additional demoisturizer includes a moisture exchanger.
 9. The device as recited in claim 1, wherein at least one of: the first demoisturizer and the second demoisturizer includes a moisture exchanger, and the device further comprising: a moisture gradient device for generating a moisture gradient, wherein the moisture gradient device is situated on a side of the moisture exchanger facing away from the closed circuit.
 10. The device as recited in claim 9, wherein the moisture gradient device includes a vacuum device for generating a vacuum.
 11. The device as recited in claim 9, the moisture gradient device includes a drying agent supply device which directs a drying agent past a moisture exchanger into a drying agent discharge device.
 12. The device as recited in claim 11, further comprising: a third demoisturizer situated between the drying agent supply device and the moisture exchanger.
 13. The device as recited in claim 12, further comprising: a fourth demoisturizer situated between the moisture exchanger and the drying agent discharge device.
 14. The device as recited in claim 13, further comprising: a fifth valve situated between the drying agent supply device and the third demoisturizer; and a sixth valve is situated between the fourth demoisturizer and the drying agent discharge device, either the third demoisturizer or the fourth demoisturizer being switchable downstream from the drying agent supply device via the fifth valve in the direction of flow, and either the fourth demoisturizer or the third demoisturizer being switchable upstream from the drying agent discharge device via the sixth valve, so that when the fluid flows from the drying agent supply device to the drying agent discharge device, the fluid flows either first through the third demoisturizer and then through the fourth demoisturizer or first through the fourth demoisturizer and then through the third demoisturizer.
 15. The device as recited in claim 13, wherein at least one of: the third demoisturizer and the fourth demoisturizer includes a moisture filter.
 16. The device as recited in claim 4, wherein the moisture filter is a zeolith filter.
 17. The device as recited in claim 1, wherein the first demoisturizer is heatable.
 18. The device as recited in claim 4, wherein the moisture exchanger is heatable.
 19. The device as recited in claim 4, wherein the moisture exchanger is a moisture-permeable diaphragm.
 20. The device as recited in claim 4, wherein the moisture exchanger includes a porous ceramic tube having a zeolith coating.
 21. The device as recited in claim 20, wherein the ceramic tube is filled with a zeolith granulate.
 22. The device as recited in claim 21, wherein the ceramic tube is made of a PTC ceramic.
 23. The device as recited in claim 1, further comprising: a compressor situated in the pipe of the closed circuit conducting the fluid.
 24. The device as recited in claim 1, further comprising: a moisture sensor situated in the bypass line.
 25. The device as recited in claim 1, wherein, at least one of the following: the fluid is a refrigerant, and the closed circuit is a refrigeration system.
 26. A method for drying fluids circulating in closed circuits, comprising: directing at least part of a fluid from a pipe of a closed circuit conducting the fluid into a bypass line connected in parallel to the pipe of the closed circuit conducting the fluid; and drying the at least part of the fluid using a drying device disposed in the bypass line, the drying device including at least one demoisturizer.
 27. A method for drying fluids circulating in closed circuits, comprising: directing at least part of a fluid from a pipe of a closed circuit conducting the fluid into a bypass line, connected in parallel to the pipe of the closed circuit, via a first valve and a second valve; and drying the at least part of the fluid using a drying device disposed in the bypass line, the drying device including: a first demoisturizer that includes a first moisture filter; and a second demoisturizer that includes a moisture exchanger, wherein the moisture filter is heated when reaching a defined moisture threshold value to drive out moisture accumulated in the moisture filter and discharge the moisture via the moisture exchanger.
 28. The method as recited in claim 27, wherein the drying device further includes a third demoisturizer disposed in the bypass line, the third moisturizer including a second moisture filter.
 29. The method as recited in claim 27, wherein a third valve is situated between the first valve and the first demoisturizer, and a fourth valve is situated between the second demoisturizer and the second valve, either the first demoisturizer or the second demoisturizer being switchable downstream from the first valve via the third valve in the direction of flow, and either the second demoisturizer or the first demoisturizer is switchable upstream from the second valve via the fourth valve, so that when the fluid flows from the third valve to the fourth valve, the fluid flows either first through the first demoisturizer and then through the second demoisturizer or first through the second demoisturizer and then through the first demoisturizer.
 30. The method as recited in claim 29, wherein, after heating the first demoisturizer for driving out the accumulated moisture, the direction of flow is reversed.
 31. The method as recited in claim 27, wherein the drying device further includes a device for generating a moisture gradient that is situated on a side of the moisture exchanger facing away from the closed circuit.
 32. The device as recited in claim 13, wherein at least one of: the first demoisturizer, the second demoisturizer, the third demoisturizer, and the fourth demoisturizer is heatable.
 33. The device as recited in claim 19, wherein the moisture-permeable diaphragm is at least one of: a Nafion diaphragm and a zeolith molecular sieve.
 34. The device as recited in claim 24, wherein the moisture sensor is disposed downstream from the first demoisturizer. 